In a charged particle radiation apparatus represented by an electron microscope, on the basis of scanning with an electron beam or the like, a microstructure is observed with high resolution using detected detection signals. With the higher resolution, influences by micro vibration, sound, electromagnetic wave, etc. from outside are becoming obvious. As measures for image defects produced based on installation environment sound, placement of a soundproof cover to surround the apparatus is considered.
By the placement of the soundproof cover, transmission of acoustic wave is blocked and, particularly, the influence by the transmission of the high-frequency acoustic wave may be suppressed. As specific structures of the soundproof cover, PTL 1 describes a method for addressing by disposing within the cover a first noise absorber which provides noise absorbing performance specialized for the natural frequency of the apparatus and a second noise absorber specialized for the frequencies of acoustic standing waves generated within the cover. Further, PTL 2 describes a soundproof cover including a cylindrical body on an inner wall. Furthermore, PTL 3 describes a method of providing an acoustic damping material having each of longitudinal, lateral, height dimensions equal to ¼ of the dimension of the cover at a corner of the cover.